The present invention relates generally to a DC plasma display panel, and more specifically to a DC plasma display panel having holes in the cathodes for confining the plasma discharge within a discrete area of a plasma display panel cell. The present invention also relates to methods of making the DC plasma display panel of the present invention.
Color plasma display panels are considered by many to be the future of large-screen TVs, mainly because high quality CRT TVs tend to be bulky, and larger projection screen TVs typically have a poor image quality and limited viewing angles. In addition, the plasma display panels are ideal for the new digital HDTV format. Currently, there are two types of color plasma display panel devices; the DC plasma display panel and the AC plasma display panel. Both the AC-type and DC-type plasma display panels operate on the same general principles. That is, a gas discharge in each individual display cell (also known as a sub-pixel) generates ultraviolet light which excites a phosphor layer that fluoresces visible light. Differing phosphors are used for the red, green and blue primary colors, and full color moving images are obtained by modulating each primary color sub-pixel to one of typically 256 intensity levels at about 60 times a second.
The AC-type color plasma display panels typically are divided into two categories; surface discharge type AC plasma display panels, and opposed discharge type AC plasma display panels.
FIG. 1 shows a typical surface discharge type AC plasma display panel 100. AC plasma display panel 100 suitably comprises a front glass substrate 102, and a rear glass substrate 104. Front glass substrate 102 comprises a plurality of display or sustain electrodes 106, and rear glass substrate 104 includes a plurality of address electrodes 108 running substantially orthogonal to sustain electrodes 106. During operation, an AC voltage source is applied to sustain electrodes 106, and the fringing electro-magnetic fields created by these excited electrodes reach into the gas in the plasma display panel cell and create a gas or plasma discharge. The discharge creates ultraviolet light which excites phosphor layers deposited on rear substrate 104. Rear substrate 104 also includes a plurality of barrier ribs 110 which separate each sub-pixel. The barrier ribs 110 prevent emitted light radiation in one display cell from seeping over into adjacent display cells, thus, reducing cross-talk between display cells.
FIG. 2 illustrates an opposed discharge type AC plasma display panel 200. As with the surface discharge type AC plasma display panel 100, opposed discharge type AC plasma display panel 200 comprises a front substrate 202 having a first electrode 206, and a rear substrate 204 having an second electrode 208 substantially orthogonal to first electrode 206. During operation of the opposed discharge type AC plasma display panel 200, an AC plasma discharge is generated between an electrically excited first electrode 206 and an electrically excited second electrode 208. The plasma discharge is generated on the surface of dielectric layer 212 and the ultraviolet light created by the discharge excites the phosphor on rear substrate 204. Opposed discharge type AC plasma display panel 200 also includes a plurality of barrier ribs 210 which help prevent the plasma discharges in each display cell from spreading to other cells in the plasma display panel.
One advantage of the AC-type plasma display panels is that they tend to have longer lifetimes than the DC-type displays because the AC-type displays include dielectric layers (112, 212) deposited on the substrates which help to protect the display electrodes from plasma discharge sputtering. However, the AC-type display panels have various limitations also. For example, even though both AC-type plasma display panels include barrier ribs for reducing cross-talk between display cells, the barrier ribs do not stop all the discharge bleeding between the cells, so the contrast ratio of the AC-type plasma display panels tends to be poor. In addition, dielectric layers (112, 212) which are deposited on the AC-type display panel substrates have a high capacitance, causing the AC-type plasma display panels to have a much slower response time than the DC plasma display panel counterparts.
Referring now to FIGS. 3 and 4, typical DC-type plasma display panels currently known in the art are shown. Specifically, FIG. 3 shows a monochrome DC plasma display panel, while FIG. 4 shows a color DC plasma display panel. As illustrated in FIG. 3, a typical monochrome DC plasma display panel 300 comprises a first substrate 302 having a plurality of rows of cathodes 306, and a second substrate 304 having a plurality of rows of anodes 308 running substantially orthogonal to cathodes 306. In DC plasma display panel 300, DC discharges are generated between electrically activated cathodes 306 and electrically activated anodes 308. Second substrate 304 of monochrome DC plasma display panel 300 further includes a plurality of barrier ribs 310 for separating anodes 308. The barrier ribs also help define the individual display cells of DC plasma display panel 300.
Color DC plasma display panel 400, as illustrated in FIG. 4, is similar to the monochrome DC plasma display panel of FIG. 3, except color DC plasma display panel 400 includes red, green and blue phosphors for generating the color display. As shown in FIG. 4, color DC plasma display panel 400 includes a front plate 402 having a plurality of cathodes 404 thereon. Color DC plasma display panel 400 further includes a rear plate 406 having a plurality of display anodes 408 thereon. Each display anode 408 is connected to a display anode bus lines 410 with a resistor 412. Covering anodes 408, anode bus lines 410, and resistors 412 is an insulating dielectric layer 414 which also covers substantially all of rear plate 406. Color DC plasma display panel 400 is made up of a large number of display cells 416 which are defined by barrier ribs 418, priming ribs 420, and cathodes 404. Within each display cell 416 is one of three types of phosphor 422; red, green or blue. Excitation of these three phosphors in a predetermined fashion creates the color display on front plate 402 of color DC plasma display panel 400.
Conventional DC plasma display panels typically utilize the abnormal glow or normal glow regions of a DC glow discharge at or below 400. Torr gas pressure. At these pressures, conventional color DC plasma display panels exhibit poor luminous efficiency and typically have low display lifetimes due to cathode sputtering. One method of improving the lifetime of the DC plasma display panel is to increase the gas pressure in the glow discharge. However, this typically causes more current to flow in the discharge cell, reducing the self-stabilizing function of the glow discharge. To reduce the discharge current at the increased gas pressures, resistors are used to limit the current flow in the discharge cells. As shown in FIG. 4, this is a well known method of creating color DC plasma display panels. However, for large sized plasma display panels, a large number of resistors (usually several million) are needed to produce a stable operating plasma display panel. Adding these individual resistors decreases the uniformity of the display panel, and complicates the plasma display panel manufacturing process.
Accordingly, it is an advantage of the present invention to provide a novel color DC plasma display panel which overcomes the shortcomings of the prior art.
Another advantage of the present invention is to provide a DC plasma display panel with holes spaced along the cathode lines for confining the glow discharge of each display cell within the cathode holes.
Yet another advantage of the present invention is to provide a DC plasma display panel which utilizes the abnormal glow region of the glow discharge, thus giving the glow discharge a self-stabilizing function without the need to limit the current within the discharge.
Still another advantage of the present invention is to decrease the cross-talk between adjacent display cells, thereby improving the contrast ratio of the plasma display panel.
Still another advantage of the present invention is to utilize hollow cathode discharge (i.e., a high efficiency discharge which arises from trapped electrons inside the hollow cathode) to obtain high luminous efficiency within the display panel.
The above and other advantages of the present invention are carried out in one form by a DC plasma display panel defined by a plurality of display cells or sub-pixels organized in a matrix configuration. The DC plasma display panel comprises a first plate having a first substrate and a plurality of rows of cathodes extending substantially along a length of the substrate. The cathodes include a plurality of holes therein spaced along each cathode row; preferably one hole for each sub-pixel. The first plate further comprises a dielectric layer which covers the first substrate and the plurality of rows of cathodes. The dielectric layer includes a plurality of holes aligned with the holes in the cathodes.
The DC plasma display panel further comprises a second plate having a second substrate and a plurality of rows of anodes extending along the length of the second substrate. In addition, the second plate includes a plurality of barrier ribs extending substantially along the length of the second substrate, parallel with the plurality of rows of anodes. The barrier ribs form channels on the second substrate and at least one of the rows of anodes is positioned within each channel formed by the barrier ribs. One or more phosphor layers are deposited in the channels.
The DC plasma display panel is formed by combining the first plate and the second plate such that the barrier ribs on the second substrate of the second plate are touching or are in substantial touching proximity with the dielectric layer on the first substrate of the first plate. In addition, the first plate and the second plate are aligned so that the channels formed by the barrier ribs and the rows of anodes on the second substrate run substantially orthogonal to the rows of cathodes on the first substrate. The display cells of the DC plasma display panel are formed at locations proximate where the channels and the rows of anodes cross the rows of cathodes, and more particularly where the rows of anodes cross the holes in the cathodes.